It is known that the formation of a hard folder comprises, after the cutting of the cardboard into frames or mirror-sections and the preparation of a backbone, the glueing of the frames and the backbone on the lining material and the beating of the protruding trasverse and longitudinal rims of said lining inwardly of the folder. Afterwards, the same folder is pressed to allow for the maximum adhesion of the cardboard to the lining.
Also known are machines for automatically carrying out the above described operations.
But such machines are constructed to carry out a complex operating procedure and, therefore, have a very high manufacturing cost which is justifiable only for large productions.